Method of manufacturing a magnetic head including a read head with read track width defining layer that planarizes the write gap layer of a write head

ABSTRACT

A method of making a magnetic head that has a read head with a track width includes the steps of depositing a read track width defining material layer on a read sensor material layer; forming a bi-layer photoresist mask on the read track width defining material layer that masks a read track width defining layer portion of the read track width defining material layer; removing by reactive ion etching (RIE) a portion of the read track width defining material layer not masked by the photoresist mask to form the read track width defining layer portion with exposed first and second side edges that are spaced apart a distance equal to the track width; removing by ion milling a first portion of the read sensor material layer not masked by the read track width defining layer portion to form a second portion of the read sensor material layer with exposed first and second side edges that have a width equal to the track width; depositing hard bias and lead material layers on the photoresist mask in contact with the first and second side edges of each of the second portion of the read sensor material layer and the read track width defining layer portion; and removing the photoresist mask, thereby lifting off a portion of the hard bias and lead material layers leaving first and second hard bias and lead layers connected to the first and second side edges of each of the second portion of the read sensor material layer and the read track width defining layer portion.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a read head that has a read track widthdefining layer that planarizes the write gap layer of a write head and,more particularly, to a read head and method of making wherein a readtrack width defining layer is located between the read sensor of theread head and the write gap layer of the write head and has a thicknesswhich substantially planarizes the read head at the level of first andsecond hard bias and lead layers which, by replication of subsequentlayers, planarizes the write gap layer.

2. Description of the Related Art

The heart of a computer is an assembly that is referred to as a magneticdisk drive. The disk drive includes a rotating magnetic disk, write andread heads that are suspended by a suspension arm above the rotatingdisk and an actuator that swings the suspension arm to place the readand write heads over selected circular tracks on the rotating disk. Theread and write heads are directly mounted on a slider that has an airbearing surface (ABS). The suspension arm biases the slider into contactwith the surface of the disk when the disk is not rotating but, when thedisk rotates, air is swirled by the rotating disk adjacent the ABS tocause the slider to ride on an air bearing a slight distance from thesurface of the rotating disk. The write and read heads are employed forwriting magnetic impressions to and reading magnetic impressions fromthe rotating disk. The read and write heads are connected to processingcircuitry that operates according to a computer program to implement thewriting and reading functions.

The write head includes a coil layer embedded in first, second and thirdinsulation layers (insulation stack), the insulation stack beingsandwiched between first and second pole piece layers. A write gap layerbetween the first and second pole piece layers forms a magnetic gap atan air bearing surface (ABS) of the write head. The pole piece layersare connected at a back gap. Current conducted to the coil layer inducesa magnetic field across the magnetic gap between the pole pieces. Thisfield fringes across the magnetic gap for the purpose of writinginformation in tracks on moving media, such as the circular tracks onthe aforementioned rotating disk, or a linearly moving magnetic tape ina tape drive.

The read head includes first and second shield layers, first and secondgap layers, a read sensor and first and second lead layers that areconnected to the read sensor for conducting a sense current through theread sensor. The first and second gap layers are located between thefirst and second shield layers and the read sensor and the first andsecond lead layers are located between the first and second gap layers.The distance between the first and second shield layers determines thelinear read density of the read head. The read sensor has first andsecond side edges that define a track width of the read head. Theproduct of the linear density and the track density equals the arealdensity of the read head which is the bit reading capability of the readhead per square inch of the magnetic media.

Rows and columns of combined read and write heads are made on a wafersubstrate located in various chambers where layers are deposited andthen defined by subtractive processes. A plurality of substrate wafersmay be located on a turntable which rotates within the chamber and whichmay function as an anode. One or more targets, which comprise materialsthat are to be deposited on the wafer substrates, may also be located inthe chamber. The target functions as a cathode and a DC or RF bias maybe applied to the cathode and/or the anode. The chamber contains a gas,typically argon (Ar), which is under a predetermined pressure. Materialis then sputtered from a target onto the wafer substrates forming alayer of the desired material. Layers may also be deposited by ion beamdeposition wherein an ion beam gun directs ionized atoms (ions) onto atarget which causes the target to sputter material on the wafersubstrate. A subtractive process may employ a gas in the chamber, suchas argon (Ar), under pressure which causes sputtering of the materialfrom portions of the wafer substrate not covered by a mask.Alternatively, the subtractive process may employ an ion beam gun thatdischarges high velocity ions, such as argon (Ar) ions, which impact andremove portions of the wafer substrate that are not covered by a mask.

First and second hard bias and lead layers are typically joined at firstand second side edges of the read sensor in what is known in the art asa contiguous junction. A first step in making this junction is forming aread sensor material layer over the entire wafer. Then, for eachmagnetic head a bilayer photoresist is formed over the desired readsensor site with a top layer portion that has first and second sideedges for defining the first and second side edges of the read sensorand a bottom layer portion directly on the read sensor material layerthat is recessed from the top layer portion so as to provide undercutsfor the purpose of lifting off subsequently deposited unwanted layerportions. The wafer is then rotated by the turntable and a subtractiveprocess, such as ion milling, is employed for removing all of the readsensor material layer except the read sensor under the bilayerphotoresist. Unfortunately, the read sensors on the outside of the waferare subjected to a different ion milling angle than wafers on the insideof the wafer, resulting in magnetic heads which have differentcharacteristics. A first side edge of the read sensors on the outside ofthe wafer is notched while a second side edge is not notched. This isdue to the fact that the turntable is rotated about an axis that is atan angle to the milling direction for the purpose of minimizingredeposition of the milled material. While the bilayer photoresist isstill in place a hard bias and lead layer material is deposited on theentire wafer substrate. The bilayer photoresist is then removed liftingoff the bias and lead layer material deposited thereon. The result isthat a first hard bias and lead layer makes good abutting engagementwith the first side edge of the read sensor, however, the second hardbias and lead layer may make only partial abutting engagement with thenotched second side edge of the read sensor. This occurs because theangle of deposition of the hard bias and lead layer material isdifferent than the angle of ion milling of the second side of the readsensor. The result is that the hard bias material adjacent the notchedside edge may not make sufficient abutting contact for magneticallystabilizing the magnetic domains of the read sensor. This would degradethe performance of the read head.

Another problem is that the undercut of the bilayer photoresist permitsion milling to mill, to some extent, under the undercut. This results inan unpredictable track width of the read sensor.

A further problem noted with the above process is that upon depositionof the hard bias and lead layer material there is some overlap of thehard bias and/or lead layer material on a top surface portion of theread sensor adjacent each of the first and second side edges. This cancause an exchange coupling between the hard bias material and the readsensor which adversely affects the magnetics of the read sensor and mayalter the expected track width of the read sensor.

Still another problem with the above process is that the first andsecond hard bias and lead layers have a higher profile than the readsensor. When the second gap, the second shield/first pole piece layerand the write gap layer of the write head are deposited there is a dipin the gap layer. This dip is known in the art as write gap curvatureand can significantly degrade the performance of the write head. With acurved write gap the write head writes curved magnetic impressions intoa rotating disk which are then read by a linearly extending read sensor.The read sensor will only read the center portion of the curvedimpression which reduces read signal performance.

SUMMARY OF THE INVENTION

The present invention provides a read and write head combination whereinthe read head is planarized so as to overcome write gap curvature. Amethod of making is also provided where a read track width defininglayer is employed for defining the track width of the read sensor withimproved side edges. In a preferred embodiment the read track widthdefining layer remains in the head for planarizing the read head andovercoming the write gap curvature problem.

In the method a read track width defining material layer is formed on aread sensor material layer. The bilayer photoresist mask is then formedfor masking the aforementioned read track width defining layer. A firstselective removing process is then employed for removing the read trackwidth defining material layer, except for the read track width defininglayer that is masked by the photoresist mask. The first selectiveremoving forms the read track width defining layer with exposed firstand second side edges. Then a second selective removing process isemployed for removing the read sensor material layer, except for a readsensor layer portion masked by the read track width defining layer. Thesecond selective removing process forms a read sensor layer with exposedfirst and second side edges. Then, hard bias and lead material layersare deposited on the photoresist mask adjacent the first and second sideedges of each of the read sensor layer and the read track width defininglayer. Finally, the photoresist mask is removed thereby lifting off aportion of the hard bias and lead material layer leaving first andsecond hard bias and lead layers connected to the first and second sideedges of each of the read sensor layer and the read track width defininglayer.

In a preferred embodiment the track width defining layer is carbon. Whenthe read track width defining layer is carbon the first selectiveremoving is preferably a reactive ion etch with an oxygen (O₂) base.Other materials for the read track width defining layer may be silicon(Si) or silicon dioxide (SiO₂). When the read track width defining layeris silicon (Si) or silicon dioxide (SiO₂) the first selective removingprocess may be a reactive ion etch with a freon (CF₄) base. In thepreferred embodiment the read track width defining layer has a thicknesswhich is the difference between the thickness of the hard bias and leadlayer and the thickness of the read sensor. With this arrangement theread track width defining layer planarizes the read head at the hardbias and lead layer level so that subsequent layers formed on the readsensor and the first and second hard bias and lead layers do notreplicate a curvature to the write gap of the write head. If desired,however, the read track width defining layer may be removed by ashing inthe presence of oxygen (O₂) within a chamber.

An object of the present invention is to provide a combined read andwrite head wherein the read head is planarized so as to obviate writegap curvature of the write head.

Another object of the present invention is to provide a read headwherein contiguous junctions are made between first and second hard biasand lead layers and first and second side edges of a read sensorrespectively wherein the first and second hard bias and lead layers donot overlap first and second surface portions adjacent the first andsecond side edges of the read sensor.

A further object of the present invention is to provide a read and writehead wherein each of first and second hard bias and lead layers make acontinuous abutting junction with precisely located first and secondside edges of the read sensor.

Still another object is to provide a method of making a read and writemagnetic head wherein a bilayer photoresist mask is employed fordefining a read track width defining layer which, in turn, is employedfor defining the read track width of a read sensor.

Still a further object is to provide a method of making a read and writemagnetic head which substantially eliminates any portion of first andsecond hard bias and lead layers covering a top surface of the readsensor, implements complete abutting engagement of the first and secondhard bias and lead layers with first and second side edges of the readsensor and planarizes the read head so that no curvature is replicatedto the write gap layer of the write head.

Other objects and advantages of the present invention will becomeapparent upon reading the following description taken together with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a planar view of an exemplary magnetic disk drive;

FIG. 2 is an end view of a slider with a magnetic head of the disk driveas seen in plane 2—2;

FIG. 3 is an elevation view of the magnetic disk drive wherein multipledisks and magnetic heads are employed;

FIG. 4 is an isometric illustration of an exemplary suspension systemfor supporting the slider and magnetic head;

FIG. 5 is an ABS view of the magnetic head taken along plane 5—5 of FIG.2;

FIG. 6 is a partial view of the slider and a prior art magnetic head asseen in plane 6—6 of FIG. 2;

FIG. 7 is a partial ABS view of the slider taken along plane 7—7 of FIG.6 to show the read and write elements of the prior art magnetic head;

FIG. 8 is a view taken along plane 8—8 of FIG. 6 with the insulationstack removed;

FIGS. 9 and 9B are block diagrams of various methods of depositing andmilling layers within a chamber;

FIG. 10 is a side elevation view of a bilayer photoresist on a readsensor material layer;

FIG. 11 is the same as FIG. 10 except ion milling has been implementedfor removing the read sensor material layer except a read sensor underthe bilayer photoresist;

FIG. 12 is the same as FIG. 11 except first and second hard bias andlead layers have been formed,

FIG. 13 is the same as FIG. 12 except a second gap layer, a secondshield/first pole piece layer, a write gap layer, a second pole tiplayer and an overcoat layer have been formed on the read sensor and thefirst and second hard bias and lead layers;

FIG. 14 is a side elevation view of a first step in the present methodof making a read head;

FIG. 15 is the same as FIG. 14 except a read track width definingmaterial layer of carbon has been formed on the read sensor materiallayer;

FIG. 16 is the same as FIG. 15 except a bilayer photoresist has beenformed on the track width defining material layer;

FIG. 17 is the same as FIG. 16 except reactive ion etching (RIE) hasbeen implemented to remove all of the track width defining materiallayer except a track width defining material layer portion (track widthdefining layer) below the bilayer photoresist;

FIG. 18 is the same as FIG. 17 except ion milling has been employed forremoving the read sensor material layer except for a read sensor layerdirectly below the track width defining layer;

FIG. 19 is the same as FIG. 18 except first and second hard bias andlead layers have been formed;

FIG. 20 is the same as FIG. 19 except the bilayer photoresist has beenremoved;

FIG. 21 is the same as FIG. 20 except the write head and additionallayers of the read head are shown;

FIG. 22 is a side view of the first and second hard bias lead layersconnected to the first and second side edges of the read sensor layerwhich is the same as that shown in FIG. 20;

FIG. 23 is the same as FIG. 22 except the track width defining layer hasbeen removed;

FIG. 24 is the same as FIG. 23 except the second gap layer, the secondshield/first pole piece layer, the write gap layer, the second pole tiplayer and an overcoat layer have been formed;

FIG. 25 is the same as FIG. 17 except silicon (Si) or silicon dioxide(SiO₂) is employed for the track width defining layer and RIE isemployed with a fluorine base as a removal process, and;

FIG. 26 is the same as FIG. 25 except ion milling is employed fordefining the first and second side edges of the read sensor layer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings wherein like reference numerals designatelike or similar parts throughout the several views there is illustratedin FIGS. 1-3 a magnetic disk drive 30. The drive 30 includes a spindle32 that supports and rotates a magnetic disk 34. The spindle 32 isrotated by a motor 36 that is controlled by a motor controller 38. Acombined read and write magnetic head 40 is mounted on a slider 42 thatis supported by a suspension 44 and actuator arm 46. A plurality ofdisks, sliders and suspensions may be employed in a large capacitydirect access storage device (DASD) as shown in FIG. 3. The suspension44 and actuator arm 46 position the slider 42 so that the magnetic head40 is in a transducing relationship with a surface of the magnetic disk34. When the disk 34 is rotated by the motor 36 the slider is supportedon a thin (typically, 0.05 μm) cushion of air (air bearing) between thesurface of the disk 34 and the air bearing surface (ABS) 48. Themagnetic head 40 may then be employed for writing information tomultiple circular tracks on the surface of the disk 34, as well as forreading information therefrom. Processing circuitry 50 exchangessignals, representing such information, with the head 40, provides motordrive signals for rotating the magnetic disk 34, and provides controlsignals for moving the slider to various tracks. In FIG. 4 the slider 42is shown mounted to the suspension 44. The components describedhereinabove may be mounted on a frame 54 of a housing 55, as shown inFIG. 3.

FIG. 5 is an ABS view of the slider 42 and the magnetic head 40. Theslider has a center rail 56 that supports the magnetic head 40, and siderails 58 and 60. The rails 56, 58 and 60 extend from a cross rail 62.With respect to rotation of the magnetic disk 34, the cross rail 62 isat a leading edge 64 of the slider and the magnetic head 40 is at atrailing edge 66 of the slider.

Merged Magnetic Head

FIG. 6 is a side cross-sectional elevation view of the merged MR or spinvalve head 40 which has a write head portion 70 and a read head portion72, the read head portion employing an MR or spin valve sensor 74. FIG.7 is an ABS view of FIG. 6. The sensor 74 is located between first andsecond gap layers 76 and 78 and the gap layers are located between firstand second shield layers 80 and 82. In response to external magneticfields, the resistance of the sensor 74 changes. A sense current I_(s)conducted through the sensor causes these resistance changes to bemanifested as potential changes. These potential changes are thenprocessed as readback signals by the processing circuitry 50 shown inFIG. 3.

The write head portion of the merged head includes a coil layer 84located between first and second insulation layers 86 and 88. A thirdinsulation layer 90 may be employed for planarizing the head toeliminate ripples in the second insulation layer caused by the coillayer 84. The first, second and third insulation layers are referred toin the art as an “insulation stack”. The coil layer 84 and the first,second and third insulation layers 86, 88 and 90 are located betweenfirst and second pole piece layers 92 and 94. The first and second polepiece layers 92 and 94 are magnetically coupled at a back gap 96 andhave first and second pole tips 98 and 100 which are separated by awrite gap layer 102 at the ABS. As shown in FIGS. 2 and 4, first andsecond connections 104 and 106 connect leads from the sensor 74 to leads112 and 114 on the suspension 44 and third and fourth connections 116and 118 connect leads 120 and 122 from the coil 84 (see FIG. 8) to leads124 and 126 on the suspension. It should be noted that the merged head50 employs a single layer 82/92 to serve a double function as a secondshield layer for the read head and as a first pole piece for the writehead. A piggyback head employs two separate layers for these functions.

After placing a wafer substrate in a chamber 150, as shown in FIG. 9,various deposition processes 152 and various subtractive processes 154may be employed in implementing the present invention. Depositionprocesses may include sputter deposition 156, magnetron sputterdeposition 158 or ion beam sputter deposition 160. The subtractiveprocesses 154 may include sputter etching 162, reactive ion etching(RIE) 164, ion beam milling 166 or reactive ion beam milling 168. Thesputter deposition 156 may include providing argon (Ar) gas and a targetof material to be deposited in the chamber 170, providing radiofrequency (rf) or direct current (dc) bias between the target and thewafer substrate 172 and sputtering the target to deposit material fromthe target on the wafer substrate 174. The magnetron sputter deposition158 may include providing a target of material to be deposited in thechamber between a magnetron and the wafer substrate 176 and thensputtering the target in the field of the magnetron to deposit materialfrom the target on the wafer substrate 178. The ion beam sputterdeposition 160 may include providing an inert gas, such as argon (Ar),krypton (Kr) or xenon (Xe), and a target of the material to be depositedin the chamber 180 and then ion beaming the target to sputter depositthe material from the target on the wafer substrate 182. The sputteretching 162 may include providing argon (Ar) gas in the chamber 184,applying rf or dc bias to the wafer substrate 186 and then sputteretching the wafer substrate 188. The reactive ion etching 164 includesplacing argon (Ar) and reactive gases in the chamber 189, applying a dcor rf bias to the wafer substrate 190 and then reactive ion etching thewafer substrate 192. The ion beam milling 166 includes grounding thewafer substrate 193 and then ion beam milling the wafer substrate 194.The reactive ion beam milling 168 may include placing an inert gas, suchas argon (Ar) or helium (He), and reactive gases in an ion beam gun 196,grounding the wafer substrate 197 and then reactive ion beaming to millthe wafer substrate 198. The chambers are placed under variouspreselected pressures in order to implement the aforementionedprocesses. Full film deposition is made without a mask, however, whenfeatures are to be formed a mask is provided with openings where thefeatures are to be formed. A mask is also employed for covering areas tobe retained when the subtractive processes 154 are employed.

FIGS. 10-13 illustrate a prior art process for making contiguousjunctions between first and second hard bias and lead layers and firstand second side edges of a read sensor, respectively. In FIG. 10 a readsensor material layer 220 may be formed on a nonconductive electricallyinsulative first gap layer (G1) 222 by depositions 156, 158 or 160 inFIG. 9A. A bilayer photoresist 224 is then formed on the read sensormaterial layer 220 that has first and second layer portions 226 and 228.The first layer portion 226 has a width that is less than the secondlayer portion 228 so as to provide the bilayer photoresist with firstand second undercuts. This bilayer photoresist may be formed by formingthe first and second layer portions 226 and 228, light exposing thesecond layer portion and developing the second layer 228 with adeveloper that also etches the first layer 226. The second layer portion228 has first and second side edges 230 and 232 that define a desiredtrack width of a subsequently formed read sensor.

In FIG. 11 the wafer substrate is subjected to ion beam milling (166 inFIG. 9B) as the wafer substrate is rotated, which removes all of theread sensor material layer except for the read sensor 232 between thefirst and second side edges 234 and 236. When a head is located near theouter perimeter of the wafer substrate the side edges 234 and 236 aresignificantly asymmetrical. This is because of an angle of incidence θwith respect to a normal to the read sensor surface and the divergenceof the beam from a source above the center of the wafer substrate. Theresult is that the second side edge 234 is milled with a large taperwhile the first side edge 236 is fairly well defined with a small taper.The problem is not as bad for heads near the center of the wafer. InFIG. 12 first and second hard bias and lead layers 238 and 240 areformed by depositions 156, 158 or 160 in FIG. 9A wherein each hard biasand lead layer has a side edge that is formed adjacent a respective sideedge of the read sensor. Unfortunately, however, the full thickness ofthe second hard bias and lead layer 238 does not make complete abuttingcontact with the second side edge 234 of the read sensor due to anotching or depression of each of the hard bias (H.B.) and lead layers238 as shown. This is also due to the angle of incidence θ and thedivergence of the beam, and is worst for heads near the outer perimeterof the wafer substrate. This reduced abutting contact can seriouslydegrade the magnetostatic coupling between the hard bias layer and theread sensor which can, in turn, affect the magnetic stabilization of themagnetic domains of the read sensor and render the read headinoperative.

In FIG. 13 the photoresist has been removed and a second gap layer 242,a second shield/first pole piece layer 244, a write gap layer 246, asecond pole tip layer 248 and an overcoat layer 250 have been formed byany of the depositions 156, 158 or 160 in FIG. 9A. Because of the higherprofile of the hard bias and lead layers 238 and 240 relative to theread sensor 232 the second gap layer 242, the second shield/first polepiece layer 244 and the write gap layer 246 make a dip which results inwrite gap curvature of the write gap layer 246. This is not desirablesince the read head reads curved magnetic impressions in a rotatingmagnetic disk which degrades read signal performance. It should also benoted that the first and second hard bias and lead layers overlap firstand second surface portions of the read sensor adjacent the first andsecond side edges 234 and 236. If the hard bias layer overlaps theseportions this results in an exchange coupling which can degrade themagnetic performance of the read sensor layer. The overlap can alsochange the track width of the read sensor. Still another problem is thatthe side edges 234 and 236 of the read sensor are not directly under theside edges 230 and 232 of the second layer of the bilayer photoresist.This results in a read sensor with an unreliable track width.

The Invention

FIGS. 14-21 illustrate various steps of the present method of making theread head. In FIG. 14 a ferromagnetic first shield layer (S1) 300 isformed on the wafer substrate (not shown), a nonmagnetic electricallyinsulative first gap layer (G1) 302 is formed on the first shield layerand a read sensor material layer 304 is formed on the first gap layer302 by any of the depositions 156, 158 or 160 in FIG. 9A. The readsensor material layer 304 may comprise multiple layers such as anantiferromagnetic pinning layer, a ferromagnetic pinned layer, anelectrically conductive spacer layer, a ferromagnetic free layer and acapping layer, which layers constitute a spin valve sensor. Theferromagnetic pinned layer may be an antiparallel (AP) pinned layer asdescribed in U. S. Pat. No. 5,018,037, which is incorporated byreference herein, or a pinned layer consisting of a single thin film.The layers can differ depending upon different types of spin valvesensors or anisotropic magnetoresistive (AMR) sensors employed. In FIG.15 a track width defining material layer 306 of carbon is formed on theread sensor material layer 304. The track width defining material layerhas a predetermined thickness which will be described in more detailhereinbelow.

In FIG. 16 a bilayer photoresist 308 is formed on the track widthdefining material layer 306 which is the same as the bilayer photoresist224 shown in FIG. 10. In FIG. 17 a reactive ion etch (RIE) with anoxygen (O₂) base, as shown in 164 of FIG. 9B, is employed in a chamber(not shown) for removing all of the track width defining material layerexcept for a track width defining layer 310 below the bilayerphotoresist 308. The chamber may contain 20% oxygen (O₂) and 80% argon(Ar) with a pressure of 5 millitorr. An rf bias of 150 watts may beapplied to the wafer substrate. We have found that the first and secondside edges 312 and 314 of the track width defining layer portion 310 aresubstantially aligned with first and second side edges 316 and 318 ofthe bilayer photoresist. This is because the RIE process is selective bya ratio of 4 to 1 to the track width defining material layer over thematerials of the read sensor material layer 304 and the bilayerphotoresist 308. Accordingly, the read track width defining materiallayer is quickly removed, except the read track width defining layer310, without any substantial removal of the read sensor material layer304 or the bilayer photoresist 308.

In FIG. 18 ion beam milling, as shown in 166 of FIG. 9B, is employed forremoving all of the read sensor material layer except for a read sensorlayer 320 directly below the read track width defining layer 310. Thismilling is selective by a ratio of 4 to 1 to the read sensor materiallayer 304 (FIG. 17) over the carbon of the read track width defininglayer 310. It should be noted from FIG. 17 that the first and secondside edges 312 and 314 of the read track width defining layer areimmediately adjacent the read sensor material layer 304 so that firstand second side edges 322 and 324 of the read sensor in FIG. 18 areaccurately located and defined with less asymmetry between the two edges322 and 324 for heads located nearest the outer perimeter of the wafersubstrate. In FIG. 19 first and second hard bias and lead layers 326 and328 are formed which have side edges that make complete abuttingengagement with respective side edges 322 and 324 of the read sensor andthe first and second side edges 312 and 314 of the read track widthdefining layer. In FIG. 20 the bilayer photoresist 308 is removedleaving top surfaces 330 and 332 of the first and second hard bias andlead layers substantially planar with the top surface 334 of the readsensor.

In order to accomplish this the thickness of the read track widthdefining layer portion 310 should be substantially the differencebetween the thickness of the hard bias and lead layers 330 and 332 andthe thickness of the read sensor 320. This thickness is preferably100-500Å and, more preferably, is about 200Å thick. The thickness ofeither the first and second hard bias and lead layers 330 and 332 istypically thicker than the thickness of the read sensor 320 so that whenthe thickness of the read sensor 320 is subtracted from the thickness ofone of the hard bias and lead layers the result will be the desiredthickness of the read track width defining layer 310. It should be notedthat each of the first and second hard bias and lead layers have aslight rise or “bird's beak” 336 and 338. It has been found that thisheight is less than 100Å, and does not affect the planarity of the readhead. In FIG. 21 the complete read head is shown with a nonmagneticelectrically insulative second gap layer (G2) 340 on the read sensor 310and the first and second hard bias and lead layers 326 and 328, a secondshield/first pole piece (S2/P1) layer 342 on the second gap layer 340, awrite gap layer 344 on the second shield/first pole piece layer 342, asecond pole tip layer 346 on the write gap layer 344 and an overcoatlayer 348 on the second pole tip layer 346 by any of the depositions156, 158 or 160 in FIG. 9A.

It can be seen that with this method of construction there issubstantially no write gap curvature of the write gap layer 344 sincethe read head is planarized at the first and second hard bias and leadlayer level by the read track width defining layer 310. Further, itshould be noted that the first and second hard bias and lead layers 326and 328 do not overlap any portion of the top surface 334 of the readsensor adjacent its first and second side edges 312 and 314.Accordingly, the magnetic properties of the read sensor 310 arepreserved as well as the desired track width.

FIGS. 22-24 illustrate various steps in an alternate construction of thepresent read head. FIG. 22 is the same as FIG. 20. If desired, the readtrack width defining layer portion 310 in FIG. 22 may be removed in FIG.23 by any suitable process such as ashing which is implemented by thepresence of oxygen (O₂) in a chamber. This removal may be desirable ifit is undesirable to have the carbon material at the ABS or if thecarbon has a substantially different coefficient of expansion than otherlayers in the head which may stress the read sensor or protrude otherlayers at the ABS under high heat conditions. After forming the secondgap layer (G2) 350, the second shield/first pole piece layer (S2/P1) 352and the write gap layer 354 it can be seen that the write gap layer 354has curvature under the second pole tip layer 356. Accordingly, thepreferred embodiment is the method shown in FIGS. 14-20 and theembodiment shown in FIG. 21 since write gap curvature has beeneliminated. However, the embodiment shown in FIGS. 22-24 has theadvantage over the read head made by the process in FIGS. 10-13 sincethe read head in FIG. 24 does not have an overlap of the first andsecond hard bias and lead layers on top surface portions of the readsensor 320.

FIGS. 25 and 26 illustrate alternate steps to the steps shown in FIGS.17 and 18. In FIG. 25 a silicon (Si) or silicon dioxide (SiO₂) materialis employed for the read track width defining layer portion 360 insteadof carbon as shown in FIG. 17. The chamber may contain 20% freon (CF₄)and 80% helium (He) under a pressure of 5 millitorr. An rf bias of 150watts may be applied to the wafer substrate. In this instance all of theread track width defining material layer is removed by reactive ionetching (RIE) with a fluorine base, such as freon (CF₆), which isselective by a ratio of 5 to 1 to the silicon (Si) or silicon dioxide(SiO₂) with respect to the read sensor material layer 304 and thephotoresist 308. In FIG. 26 ion beam milling is employed for definingthe first and second side edges 322 and 324 of the read sensor 320. Therate of ion beam milling of the read sensor material layer with respectto the read track width defining layer 360 and the photoresist layer 308is about 1/1.

Clearly, other embodiments and modifications of this invention willoccur readily to those of ordinary skill in the art in view of theseteachings. Therefore, this invention is to be limited only by followingclaims, which include all such embodiments and modifications when viewedin conjunction with the above specification and accompanying drawings.

We claim:
 1. A method of making a magnetic head that has an air bearingsurface (ABS) and a read head with a track width, comprising: depositinga nonmagnetic electrically insulative first gap layer; depositing a readsensor material layer on the first gap layer; depositing a read trackwidth defining material layer on the read sensor material layer; forminga bi-layer photoresist mask on the read track width defining materiallayer that masks a read track width defining layer portion of the readtrack width defining material layer; removing by reactive ion etching(RIE) a portion of the read track width defining material layer notmasked by the photoresist mask to form said read track width defininglayer portion with exposed first and second side edges that are spacedapart a distance equal to said track width; removing by ion milling afirst portion of the read sensor material layer not masked by the readtrack width defining layer portion to form a second portion of the readsensor material layer with exposed first and second side edges that havea width equal to said track width; depositing hard bias and leadmaterial layers on the photoresist mask in contact with the first andsecond side edges of each of the second portion of the read sensormaterial layer and the read track width defining layer portion; andremoving the photoresist mask, thereby lifting off a portion of the hardbias and lead material layers leaving first and second hard bias andlead layers connected to the first and second side edges of each of thesecond portion of the read sensor material layer and the read trackwidth defining layer portion.
 2. A method of making a magnetic head thathas an air bearing surface (ABS) and a read head with a track width,comprising: depositing a nonmagnetic electrically insulative first gaplayer; depositing a read sensor material layer on the first gap layer;depositing a read track width defining material layer on the read sensormaterial layer; forming a bi-layer photoresist mask on the read trackwidth defining material layer that masks a read track width defininglayer portion of the read track width defining material layer; firstselectively removing a portion of the read track width defining materiallayer not masked by the photoresist mask to form said read track widthdefining layer portion with exposed first and second side edges that arespaced apart a distance equal to said track width; second selectivelyremoving a first portion of the read sensor material layer not masked bythe read track width defining layer portion to form a second portion ofthe read sensor material layer with exposed first and second side edgesthat have a width equal to said track width; depositing hard bias andlead material layers on the photoresist mask in contact with the firstand second side edges of each of the second portion of the read sensormaterial layer and the read track width defining layer portion; removingthe photoresist mask, thereby lifting off a portion of the hard bias andlead material layers leaving first and second hard bias and lead layersconnected to the first and second side edges of each of the secondportion of the read sensor material layer and the read track widthdefining layer portion; the read track width defining layer portionbeing carbon; said first selective removing being a reactive ion etchwith an oxygen (O₂) base; and said second selective removing being ionmilling.
 3. The method as claimed in claim 2 further comprising thesteps of: before the step of depositing the first gap layer, forming aferromagnetic first shield layer; said step of depositing the first gaplayer forming the first gap layer on the first shield layer; forming anonmagnetic electrically insulative second gap layer on the read trackwidth defining layer portion, the first and second hard bias and leadlayers; and forming a ferromagnetic second shield layer on the secondgap layer.
 4. A method as claimed in claim 3 further comprising thesteps of: employing the second shield layer as a first pole piece layerfor a write head; forming a nonmagnetic electrically conductive writegap layer on the first pole piece layer that forms a portion of saidABS; forming an insulation stack with at least one coil layer embeddedtherein on the first pole piece layer; and forming a second pole piecelayer on the write gap layer at the ABS, on the insulation stack in ayoke region and connected to the first pole piece layer at a back gapregion that is recessed from the insulation stack in a direction awayfrom the ABS.
 5. The method as claimed in claim 4 wherein the read trackwidth defining layer portion is 100-500Å thick.
 6. The method as claimedin claim 5 wherein the read track width defining layer is 200Å thick. 7.The method as claimed in claim 5 wherein the first gap layer is carbon.8. A method of making a magnetic head that has an air bearing surface(ABS) and a read head with a track width, comprising: depositing anonmagnetic electrically insulative first gap layer, depositing a readsensor material layer on the first gap layer; depositing a read trackwidth defining material layer on the read sensor material layer; forminga bi-layer photoresist mask on the read track width defining materiallayer that masks a read track width defining layer portion of the readtrack width defining material layer; first selectively removing aportion of the read track width defining material layer not masked bythe photoresist mask to form said read track width defining layerportion with exposed first and second side edges that are spaced apart adistance equal to said track width; second selectively removing a firstportion of the read sensor material layer not masked by the read trackwidth defining layer portion to form a second portion of the read sensormaterial layer with exposed first and second side edges that have awidth equal to said track width; depositing hard bias and lead materiallayers on the photoresist mask in contact with the first and second sideedges of each of the second portion of the read sensor material layerand the read track width defining layer portion; removing thephotoresist mask, thereby lifting off a portion of the hard bias andlead material layers leaving first and second hard bias and lead layersconnected to the first and second side edges of each of the secondportion of the read sensor material layer and the read track widthdefining layer portion; the read track width defining portion beingsilicon (Si) or silicon dioxide (SiO₂); the first selective removingbeing a reactive ion etch with a chlorine base; and said secondselective removing being ion milling.
 9. The method as claimed in claim8 further comprising the steps of before the step of depositing thefirst gap layer, forming a ferromagnetic first shield layer; said stepof depositing the first gap layer forming the first gap layer on thefirst shield layer; forming a nonmagnetic electrically insulative secondgap layer on the read track width defining layer portion, the first andsecond hard bias and lead layers and the second gap layer; and forming aferromagnetic second shield layer on the second gap layer.
 10. Themethod as claimed in claim 9 further comprising the steps of: employingthe second shield layer as a first pole piece layer for a write head;forming a nonmagnetic electrically conductive write gap layer on thefirst pole piece layer that forms a portion of said ABS; forming aninsulation stack with at least one coil layer embedded therein on thefirst pole piece layer; and forming a second pole piece layer on thewrite gap layer at the ABS, on the insulation stack in a yoke region andconnected to the first pole piece layer at a back gap region that isrecessed from the insulation stack in a direction away from the ABS. 11.The method as claimed in claim 10 wherein the read track width defininglayer portion is 100-500Å thick.
 12. The method as claimed in claim 11wherein the read track width defining layer is 200Å thick.
 13. Themethod as claimed in claim 11 wherein the first gap layer is carbon. 14.A method of making a magnetic head that has an air bearing surface (ABS)and a read head with a track width, comprising: depositing a nonmagneticelectrically insulative first gap layer; depositing a read sensormaterial layer on the first gap layer; depositing a read track widthdefining material layer on the read sensor material layer; forming abi-layer photoresist mask on the read track width defining materiallayer that masks a read track width defining layer portion of the readtrack width defining material layer; first selectively removing aportion of the read track width defining material layer not masked bythe photoresist mask to form said read track width defining layerportion with exposed first and second side edges that are spaced apart adistance equal to said track width; second selectively removing a firstportion of the read sensor material layer not masked by the read trackwidth defining layer portion to form a second portion of the read sensormaterial layer with exposed first and second side edges that have awidth equal to said track width; depositing hard bias and lead materiallayers on the photoresist mask in contact with the first and second sideedges of each of the second portion of the read sensor material layerand the read track width defining layer portion; removing thephotoresist mask, thereby lifting off a portion of the hard bias andlead material layers leaving first and second hard bias and lead layersconnected to the first and second side edges of each of the secondportion of the read sensor material layer and the read track widthdefining layer portion; before the step of depositing the first gaplayer, forming a ferromagnetic first shield layer; said step ofdepositing the first gap layer forming the first gap layer on the firstshield layer; after removing the photoresist mask removing the readtrack width defining layer portion; forming a nonmagnetic electricallyinsulative second gap layer on the read sensor portion, the first andsecond hard bias and lead layers and the first gap layer; and forming aferromagnetic second shield layer on the second gap layer.
 15. Themethod as claimed in claim 14 further comprising the steps of: employingthe second shield layer as a first pole piece layer for a write head;forming a nonmagnetic electrically conductive write gap layer on thefirst pole piece layer that forms a portion of said ABS; forming aninsulation stack with at least one coil layer embedded therein on thefirst pole piece layer; and forming a second pole piece layer on thewrite gap layer at the ABS, on the insulation stack in a yoke region andconnected to the first pole piece layer at a back gap region that isrecessed from the insulation stack in a direction away from the ABS.